1. Modern Studies of the Atom

2. Hideki Yukawa Theorized that a particle passes back and forth between protons and neutrons to hold the nucleus together.
Predicted the existence of a particle called a meson (also known as pions). The meson was observed in 1947.

3. Cs → Ba + e− + ν (beta decay)
Enrico Fermi Theorized that a neutral particle is emitted during beta decay which he called the neutrino.
Cs →  Ba  +  e−  +  ν (beta decay)
electron
neutrino
Neutrino- tiny neutron – Observed in 1956

4. Radioactive Decay
_________
Alpha
_______
Beta
_____
Gamma

5. Paul Dirac -late 1920s Theorized that electrons should be expected in two energy states, one positive and one negative. He called these antiparticles.
Antiparticles-Mirror image of each particle. Particle have the same mass but the opposite charge.(ie: electron and positron)

6. Annihilation
Depends on frequency
When Matter meets antimatter annihilation occurs. Energy and radiation is given off.

7. Pair Production
When gamma rays pass close to nucleus, a particle and antiparticle are formed.(requires 1.02MeV or more of energy)

8. The Standard Model Matter Hadrons Leptons Particles made of quarks
Baryons
3 Quarks
Mesons
2 quarks
Leptons
Particles made of
quarks
electrons
Protons and neutron

9. QUARKS Fundamental particle of the standard model. 6 types or flavors.
Have charge.
Can’t exist on their own.
Make up Baryons and Mesons.

10. TERMS
Hadrons- anything composed of quarks Mesons-subatomic particles composed of a quark and antiquark. Baryons- particles formed by three quarks. Includes protons and neutrons. Leptons- Doesn’t have quarks. Includes electrons, muons, Tau, neutrino and antiparticles.

11. QUARKS Down(d) -1/3 Charm (c) +2/3 Strange(s) -1/3 Top (t) +2/3
Up (u) /3
Down(d) -1/3
Charm (c) +2/3
Strange(s) -1/3
Top (t) /3
Bottom (b) -1/3

12. DATES OBSERVED up- 1964 Down- 1964 Strange- 1964 Charm-1975 Bottom- 1977 Top- 1995

13. Neutrons are made of 2 down quarks and one up quark. (udd)
(+2/3) + (-1/3) + (-1/3) = 0
Protons are made of 2 up quarks and one down quark.
(uud)
(+2/3)+(+2/3)+(-1/3) = +1

15. Strong Force-Short range force that holds quarks together to form protons and neutrons in the nucleus.
Electromagnetic force- Attractive and repulsive force between charges. Binds the electrons to the nucleus.

16. Weak Force- Responsible for formation of elements and release of nuclear energy and beta decay.
Gravitational force-Weakest of four forces. Force due to the mass of the atom.

18. Gluon- the exchange particle between quarks

19. Higgs Boson
Higgs Boson- subatomic particle with zero electric charge and mass greater than zero. Its thought to interact with other particles to give them mass.
Observed at CERN on July 4th, 2012.
The Higgs boson would help explain the origin of mass in the universe. The Higgs boson completes the standard model.

20. PARTICLE ACCELERATORS
Cyclotron- E.O. Lawrence accelerated protons to a very high speed and projected them into a stationary target.

21. Synchrotron
Similar to a Cyclotron. Particle experience a higher magnetic field therefore moves at a higher speed.
Fermi National Accelerator Lab- Batavia Illinois-
Tevatron- 4miles wide- Accelerates protons to 99.9% speed of light. Uncovered the top quark

22. Linear Accelerator
Particles are accelerated as they pass through a series of conductors.
Longest is in Palo Alto California. Its 3.3 km long and buried 7.6m underground.

23. Particle Colliders
Instead of a stationary target, this aims two high speed particles at each other and detects particles that are emitted.
CERN- French-Swiss collider that is sponsored by 19 European countries in hopes of locating the Higgs-Boson particle. (17miles wide and 574ft deep)

24. Standard Model Limitations

25. The standard model doesn’t predict the mass of the fundamental particles that make up luminous matter.
Doesn’t predict the existence of dark matter
Key particles have not been directly observed. Their existence is inferred by experimental observations.
1% discrepancy in how the neutrino behaves. Due to results, they feel there may be an unknown force or particle influencing it.

26. Dark Matter
Dark matter is matter that doesn’t emit or scatter light or other electromagnetic radiation. It cannot be directly detected. Dark matter is believed to make up 83% of the matter in the universe and 23% of the mass-energy.
Regular Matter makes up only 17% of all matter.

27. Dark Matter is not…. Is not in the form of mass that we see.
is not made up of baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them.
dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter.

28. Unanswered questions Is there only one type of Higgs Boson?
Are protons absolutely stable? If not, then what is the proton‘s half-life?
Why is there now more detectable matter than antimatter in the universe?
What governs the transition of quarks and gluons into mesons and baryons?

29. What is the nature of the nuclear force that binds protons and neutrons into stable nuclei or rare isotopes?